On the Qandidate.com blog there's a new post showing you an easy way to debug HHVM applications via the built-in debugging tool and it's command line interface. The HHVM is the virtual machine version of the HipHop compiler Facebook created to speed up PHP execution.
In the previous parts of this series we got you started with HHVM and showed how we could get the symfony standard edition running on HHVM. This time we will dive deeper into HHVM by using it to debug our application. For most people the easiest way of debugging a PHP application is to place var_dump() and die() statements all over the code. Another option is installing xdebug, which has gotten a lot easier nowadays due to IDE integrations.
To illustrate, they create a super simple PHP script and show how to start up the HHVM in debug mode. They introduce you to the commands you'll need to step through the script execution and locate the breakpoints where errors are happening. You can do things like print out the current values of variables, set conditional breakpoints and get a stack trace for the execution so far.